High voltage circuit breaker



April 29, 1941.

R.-R. Prr'rMAN Erm. 2,239,829

HIGH VOLTAGE CIRCUXT BREAKER Filed Jan. 5, 1938 2 Sheets-Sheet 1 April29, 1941. R. R. PITTMAN Erm. 2,239,829

HIGH VOLTAGE CIRCUIT BREAKER Filed Jan. 5, 1938 2 sheets-sheet 2INVENTORS @a @Vm @MALI-Lm Patented Apr. 29, 1941 UNITED STATES PATENTOFFICE HIGH VOLTAGE CIRCUIT BREAKER Ralph R.. Pittman and Carroll H.Walsh, Pine Bluff, Ark.

This invention relates to high voltage circuit breakers for use inconnecting and disconnecting electrical apparatus respectively to andfrom high voltage overhead circuits, and particularly to an automatictrip-free open type of breaker, embodying a. thermally responsiveelement, which is suitable for use in connecting and protectingdistribution transformers connected to these circuits.

Because of the fact that heretofore no suitable circuit breaker has beenavailable for this purpose, the high tension windings of distributiontransformers have been and are now generallyy connected to overhead highvoltage Icircuits through expulsion fuses. Such fuses are unsatisfactoryfor the reason that a new fuse element is required after each operationof the fuse, and also because the current-time curve of the fuse doesnot follow that of the connected transformer. Low amperage fuse linksare required for this service because of the high voltage, and suchlinks are susceptible to blowing from harmless transient currents, andare generally mechanically weak.

Present available types of circuit breakers which are satisfactory forthis purpose exceed the cost of the distribution transformers in manycases, and are therefore too expensive for general use, both as to priceand as to cost of mounting.

To provide a suitably inexpensive breaker of desired effectiveness,thesolution of several problems, representing the principal objects ofthe present invention, was necessary.

The first oi these objects is the provision in a high voltage circuitbreaker of a thermally responsive element capable of relativelylargemovement in response to moderate current, that is, an element whichmoves sufficiently to trip the breaker in response to small change intemperature.

Another object is the provision of means for preventing the tripping ofthe breaker due to changes in ambient temperature, since-the ther-Inally responsive element is actuated by a small change in temperaturedue to current therethrough.

Another object is the provision of means for shunt-circuiting thethermally responsive element when it has moved sufficiently to trip thebreaker, since the element, being necessarily responsive to lowcurrents, is liable to fusing at very highv currents.

Another object is to provide means for interrupting the circuit withinan expulsion chamber or tube in response to an over-current through thebreaker.

Another object is the provision of means for removing from the circuitthe expulsion tube in which the circuit is interrupted, to therebyprevent damage to the tube from creepage current, and to definitelyvisually indicate the open position of the breaker.

'I'hese and other objects will be apparent from the followingdescription and claims taken in connection with the accompanyingdrawings forming a part of this application, in which:

Fig. 1 is a side elevational view of the invention.

Fig. 2 is a side elevational view of the device without the mounting,shown partly in section.

Fig. 3 is an upper end view'of the device without the mounting.

Fig. 4 is an enlarged sectional view taken along the line IV-IV of Fig.2.

Fig. 5 and Fig. 6 are vfragmentary views of the upper end of theremovable portion of the device.

Fig. '7 is a sectional view taken along the line VII-VII of Fig. 5.

Fig. 8 is a sectional view tafken along the line VIII-VIII of Fig. 6.

Referring first to Fig. 1, the mounting of the device includes the baseIl), having rigidly mounted thereon the spaced insulators II and I2. Anoutwardly extending weather hood I5 is secured to the outer end of theupper insulator II by means of the cap screw I6, and a connector I4 issuitably secured, as by welding, to the upper surface of the top of theweather hood I5, for the purpose of electrically 4connecting thereto aline wire I3. The upper conducting terminal I8 is pivotally mounted forrotation about the pivot II within the weather hood I5, and an upperterminal spring I9 is interposed between these members for urging theouter end of the terminal I8 in a downward direction, the extent of thisdownward movement being limited by the stop 89. Thel outer or forwardend of the terminal I8 is provided with an enlarged downwardly extendingportion for engaging and latching a cooperating contact, as will beexplained later in lincre detail.

'I'he lower or load terminal 20 is rigidly secured to the outer end ofthe lower insulator I2, and has suitably secured thereto the connector22, for electrically connecting the load conductor 2I to the terminal20. The terminal 20 is substantially U-shaped, extending outwardly fromthe insulator I2, and at its lower outer end is provided with anintegral pair of hooks, 23, 23.

The tubular insulating member, or expulsion tube of insulating material24 is arranged to span `the terminals' Il and 2l. A metal sleeve 80 istightly pressed over the tube 24 at its lower end, and a pair of pins3l, 3l extend outwardly from the sleeve along a diameter, the pins 8ifitting into and being arranged for rotation in the hooks 23, 23: themetal sleeve 30 thus providing a lower removable contact lfor the tube24. An outwardly extending metal bracket 32, securedto the sleeve 80 bymeans of the cap screw 83, has pivotally mounted at its outer end forrotation about the pivot 35, the metal lever 54. A portion of the lever34 extends upwardly above the pivot 86, and a tension spring I5, havingone end secured to the upwardly extending portion and the other to thebracket `82, constantly urges the lever B4 is a counter-clockwisedirection about the pivot 88. The lever 54 extends to a point near thebottom of the tube 24, and is there provided with a laterally extendinggrooved portion 31 for en.- gaging a flexible conductor 25 which extendsfrom the tube 24, and the thumb screw connector 88 provides means forsecuring the end of the conductor 25 to"the bracket l2, the yarrangement'being such that the spring l5 is constantly biasing the conductor 25 ina direction to extract it from the tube. w

A hollow metal sleeve 25, havingA a portion thereof fitted over theupper end of the tube 24, is rigidly attached to the tube 24 by means ofthe pins 21 and 23, and is provided with an integral eye 3| forconvenience in manipulating the device. A removable metal plug 29 isscrewed through a threaded opening between the ends of they sleeve 25andso positioned as to compress the upper end of the conductor 25 betweenthe threaded plug 23 and the metal plug 30, the latter being slidablyiitted into an opening opposite the threaded plug.

At the upper end of the sleeve 25 is mounted the insulating member 33,the lower end thereof extending downwardly into the sleeve and beingrigidly secured thereto by the pin 45 to tightly close the upper end ofthe tube 24. A metal cap 44 is fitted over the upper end of theinsulating member 39 in insulatedY spaced relation with the sleeve 25,being secured thereto by 'the pin 46, and provided with the outwardlyextending portion 41. At the outer end of the outwardly extendingportion 41 of the cap 44 is pivotally mounted the yoke shaped up'percontact 3l, shown in Fig. 3. 'I'he two arms of the yoke, 4|, 42, extendlaterally downward across the sleeve 25 and in spaced insulated relationthereto, and the stem of the yoke extends upwardly and outwardly fromthe pivot 43. A metal latch member 32, pivotally mounted on the sleeve25 by means of the pivot 33, carries a pair of insulating rollers'zs, u,mounted onine pins u, u, and :ne

so positioned as to engage the upper surface of the ends of the arms ofthe yoke 33 'when the latch member is in a vertical podtion. Under thiscondition, the tube 24 is latched in the-closed position shown in Fig. 1by the engagement. of

against the conductor 25 and the upper end of the latch member 32 in aclockwise direction.

It will be apparent from the above description that a clockwise movementof the latch member 32 about the pivot 33 will release the upper end ofthe conductor 25 and allow the contact 3l to move downwardly and out ofengagement with` the upper terminal il,

It will also be apparent, in the arrangement described, that the upperterminal spring Il may apply a very large downward pressure against thecontact 33 to assure high conductivity. without increasing the pressureof the upper end of the latch member 32 against the latch detent 11,since the downward pressure on the member 38 is transmitted about thepivot 43 through the yoke arms 4I and 42 so that the resultant forceapplied to the latch member 32 is in a vertical direction, and notlaterally against the detent 11.

Movement of the latch member 32 is normally prevented .by the engagementof its upper end with the latchfdetent 11, the latter being rigidlysecured, by means of the rivets 1 5 and 1l, Fig. 4, to the closed end ofa thermally responsive element mounted at the upper end of the tube, thedetent 11 being insulated from the element by means of the insulatingmember 12, and the insulating tubes 13 and 14. It will now be apparentthat an upward movement of `the latch detent 11 due to movement of thethermally responsive element will permit a clockwise movement of thelatch member 32, and result in the extraction of the conductor 25 fromthe tube 24, the tube and the members lattached thereto taking the openposition indicated by the broken lines of Fig. 1.

'Ihe breaker being in the open position, the latch member 32, followingthe cooling of the bimetallic element, may again be latched against thelatch detent 11, and the conductor 25 reinserted and clamped in itsoriginal position by manipulation of the threaded plug 29. By means ofan insulated switch stick cooperating with the eye 3|, the tube 24 maybe rotated back to the closed position. In the event a fault exists inthe connected circuit, the latch member 32 is immediately unlatched, andthe conductor 25 released at its upper end and extracted from the tube24,- thus interrupting the faulty circuit. Since the eye 3l is formed asa part of the sleeve 2B, the circuit interruption cannot be prevented bymanipulation of the device as described; in other words, the device isof that type commonlyY known as ftrip-free.

The thermally responsive element embodies several novel features, andits mounting and relation to the circuit are shown in Figs. 3, 4, 5, 8,'7, and 8. The element itself includes three pairs of bixnetallic-strips which bend in response to temperature change; an upper pair,l 59and 5I, joined at their outer adjacent ends by the member 61, Fig. 4; anintermediate pair 51 andv 5l, positioned below and parallel to the upperpair and having adjacent ends thereof electrically connected andmechanically joined to the open ends of the strips 59 and 50 `throughthe spacers 65 and E6 by the rivets 83 and 54, respectively; and a lowerpair 55 and 55, extending along and spaced from the intermediate pair,and having :their outer adjacent ends electrically connected andmechanically joined to the remaining ends of the intermediate pairthrough the spacers 1l and 19; the remaining adjacent ends of the lowerstrips being mechanically ,secured to the out- Wardly extending portionof the cap 44 by means of the screws 6I and 62, Fig. 8.

This ligure also illustrates the manner in which the strips 55 and 56are insulated to provide an electrical circuit through the element. Theupwardly extending portion 48 of the sleeve 26 supports the strip 56,and is electrically connected therewith, while the strip 55 is insulatedfrom the portion 48 by means of the spool-shaped insulatorr 49, butelectrically connected to the upper contact 38 through a. portion of thecap 44. The rivet 50 maintains the insulation in rigid assembledrelation with the portion 48 to provide mechanical stability.

The electrical circuit through the breaker in the normal closedposition, from the terminal I8, includes serially the contact 38, theoutwardly `extending portion of the cap 44, the lower strip 55, theintermediate strip51, the upper strip 59, thence across the end portionto the upper strip 60, 'the intermediate strip 58, the lower strip 56,the portion 48 of the sleeve 26, the flexible conductor 25, and thelower contact 88.

We have found .that the zigzag arrangement of strips herein described,when mounted as disclosed herein, provides a relatively large movementat the detent 11 in response to relatively small currents, which isdesirable for successful operation of the device under small currents athigh voltages. an arrangement is very susceptible 'to ambienttemperature change, and for this reason the incorporation in the elementof some means for ambient temperature compensationis desirable.

This we have accomplished by making the interf mediate strips 51 and 58of larger section and lower resistance than the upper and lower pairs,as shown in Fig; 7, and arranging the strips, so that, when bent due tochange in temperature, the concave sides of all thestrips face in thesame direction.

Fig. 6 illustrates a position of the members of the thermally responsiveelement when carrying normal current, and Fig. the position whencarrying an over-load current. It may be noted that the intermediatestrip 51, because of its comparatively low resistance, is substantiallyundeflected, while the deflection due to the upper and lower higherresistance strips is very apparent. It may also be observed thatdeflection of the intermediate strips due to rise in ambient temperaturewill necessitate greater deflection of the upper and lower strips tounlatch the device, thus compensating for ambient temperature.

The rate of movement of the bimetallic element, or the time required forsuflicient movement to trip the breaker, is preferably slightly shorterthan the time required for an overload on a connected transformer tocause thermal damage. Fuse elements now employed to connect distributiontransformers must carry such overloads for a short time as do not damagethe transformer, in order to prevent fusing due to short timeover-loads, such as may be due to motor-starting currents. Under thiscondition, the transformer may be seriously damaged on small continuousover-loads which do not cause fuse blowing. Our bimetallic element,however, may be made to follow the transformer heating curve for allconditions of loading and ambient temperatures, and thus provide a muchhigher degree of both protection and utilization of the transformersconnected through our circuit breaker.

We havealso found that such through the thermally responsive elementunderv given ambient temperatures, the element will Dueto the fact thathigh values of current are available from high voltage circuits,together with the fact that high resistance strips are embodied in thethermally responsive element, some means for preventing thermal damagefrom overheating by high currents is desirable in our breaker. This isaccomplished by means of a pair of low resistance metal members 5| and52, having one pair of adjacent ends electrically connected andmechanically secured respectively to the members 48 and 44, and havingmounted hereon, by means .of the rivets 68 and 69, the contacts 53 and54 at the other pair of ends, as shown in Figs. 4 and 7. The contacts 53and 54 are positioned in the path of movement of -the conduct- 'v ingbar 61, which is rigidly secured to the outer closed end of thebimetallic element by the rivets 15 and 16, Fig. 4, the bar beinginsulated from the bimetallic strips by the insulating spacer 1|, andthe insulating tubes 13 and 14. The relation of these elements is suchthat the contact bar 81 engages the contacts 53 and 54 whenever thethermally responsive element has moved sufficiently to disengage thelatch member 32 from the latch detent 11, as shown in Fig. 5. rIlhethermally responsive element is thus shunt-circuited, and undamaged bycurrent which may pass through the breaker for the time necessary toelongate and extinguish the circuit-interrupting arc within theexpulsion tube 24.

It will be apparent. from the above description that in response to apredetermined current move to disengage the latch member, and beshunt-circuited by this movement, that the conductor 25 will beextracted from the tube 24, the contact 38 will be disengaged from theterminal I8, and the circuit breaker actuated from the closed positionto the open position.

Although this invention has been shown in only one form it will beevident to those skilled in the art that many other forms andmodifications may be employed without departing from the spirit of thisinvention as described above or as set forth in the following claims.

We claim as our invention:

1. A high voltage circuit breaker comprising spaced terminals, a hollowtube of insulating material spanning said terminals and movable betweenclosed and open positions, means including a conductor within said tubeand a bimetallic element externally mounted on said tube forelectrically connecting the terminals, latch means cooperating with saidbimetallic element for maintaining said tube in the closed position,means biasing said tube to the open position, and means responsive to amovement of said bimetallic element for unlatching said tube, saidbimetallic element embodying ambient temperature compensating meanswhereby said movement is substantially dependent only upon the magnitudeof current therethrough.

2.'A high voltage circuit breaker comprising spaced terminals, a hollowtube of insulating material spanning said terminals and movable betweenclosed and open positions, means including a conductor within said tubeand a bimetallic element externally mounted on said tube forelectrically lconnecting the terminals, latch means cooperating withsaid bimetallic element for maintaining said tube in the closedposition, means biasing said tube to the open position, means rcleasablyholding said conductor and resilient means urging the retraction of saidconductor from said tube, and means responsive to a movement oi saidbimetallic element for' contemporaneously unlatching said tube andreleasing said conductor, said bimetallic element em-A operating withsaid bimetallic element -for maintaining said tube in the closedposition, means `biasing said tube to the open position, and meansresponsive to` a movement of said bimetallic element for unlatching saidtube, said bimetallic element embodying ambient temperature compensatingmeans whereby said movement is substantially dependent only upon themagnitude of current therethrough, and means for shuntcircuiting saidelement in response to coitinued movement thereof in the direction tounlatch' said tube.

4. A high voltage circuit breaker comprising spaced terminals, a hollowtube of insulating material spanning said terminals and movable betweenclosed and open positions, means including a conductor within said -tubeand a bimetallic element externally mounted on said tubei'orelectrically connecting the terminals, latch means cooperating with saidbimetallic element for maintaining said tube in the closed position,means biasing said tube to the open position, means releasably holdingsaid conductor and resilient means urging the retraction of saidconductor from said tube, means responsive to a movement of saidbimetallic element for contemporaneously unlatching said tube andreleasing said conductor, said bimetallic element embodying acompensating member substantially unaffected by current and relativelygreatly affected by ambient temperature,` and means'for shuntcircuitingsaid element in response to continued movement thereof in the directionto unlatch said tube.

5. A circuit breaker comprising spaced upper and lower terminals, a tubeof insulating material having upper and lower contacts adjacent itsrespective ends arranged to engage and disengage said terminals, acurrent responsive element assoctated with said tube, resilient meansbiasing slid tube to the disengaged position, a conductor extendingupwardly through said tube from the lower contact, resilient meansurging the withdrawal of said conductor from said tube, a slidablemember arranged to engage said conductor at its upper end, a detentcarried by said current responsive element. a swingably movable latchmember carried by said tu and engaging said detent, and common resllienmeans for biasing said latch member against said detent and saidslidable member against said conductor.

6. A circuitbreaker comprising spaced upper and lower terminals, a tubeo! insulating material having upper and lower contacts adjacent itsrespective ends arranged to engage and disengage said terminals, acurrent responsive element associated with said tube. resilient meansbiasing said tube to the disengaged position, a conductor extendingupwardly through said tube Vfrom the lower contact, resilient meansurging tl withdrawal of said conductor from said tube.

having upper and lower contacts adjacent its re-` spective ends arrangedto engage and disengage said terminals, a current responsive elementassociated with said tube, resilient means biasing said tube to thedisengaged position, a conductor extending upwardly through said tubefrom the lower contact, resilient means urging the withdrawal of saidconductor from said tube, a slidable member arranged to engage saidconductor at its upper end, a detent carried by said current responsiveelement, a latch member swingably mounted on said tubeand engaged withsaid detent. and a-spring interposed between said latch member and saidplug for concurrently urging said latch member against said detent andsaid slidable memberagainst said conductor,

8. A circuit breaker comprising spaced upper and lower terminals, a tubeof insulating material having upper and lower contacts adjacent itsrespective ends arranged to engage and disengage said terminals, saidupper contact being pivotally movable into and out oi' engagement withsaid upper terminal independent oi movement of said tube. a currentresponsive element associated with said tube, a detent carried by saidcurrent responsive element, a swingably mounted latch member engagedwith said detent, a conductor extending upwardly through said tube fromthe lower contact, a slidable member arranged to engage said conductorat its upper end, a common spring urging said slidable member againstsaid conductor and said latch member against said detent, meansresponsive to a movement of said detent away from said latch memberiorrelaxing said spring, and means dependent upon said movement forconcurrently withdrawing said conductor from said tube and actuatingsaid upper contact to the disengaged position. A

9. In a circuit breaker having an open and a closed position, athermally responsive element comprising a group of at least threebimetallic 'strips assembled in substantially parallel relationship andarranged in series circuit relation, said three strips consisting of twooutside strips and one intermedtate strip, said intermediate striphaving a resistance substantially less than that of said outside strips,said strips bending in re-4 sponse to the passage of currenttherethrough and beingarranged so that the concave sides o! said outsidestrips face respectively toward and away from said intermediate strip,means i'or electrically vconnecting said element in the circuit. meansoperable in response to a movement of said element for actuating saidbreaker from the closed to the open position, and means responsive tosaid movement for shunt-circuiting said element.

10. In a circuit breaker having an open and a closed position, athermally responsive element comprising a series circuit arrangement o!at i least three bimetallic strips mechanically joined in zigzagrelation to one another, there being two outer strips and one stripinterposed therebetween, nid strips bending in resronse to passage ocurrent theretlncugh and being so arranged that 'the concave vsides ofsaid outer strips face respectively toward and away from saidintermediete strip, means electrically connecting said element in the'circuit, means operable in response to a movement of said element foractuating said breaker from the closed to theopen position, and meansresponsive to said movement for shuntcircuiting said element.

1l. In a circuit breaker, a. thermally responsive element comprising agroup oi at least Ithree blmetallic strips assembled in substantiallyparallel relationship and in series' circuit arrangement, there beingtwo outside strips and one intermediate strip, said intermediate striphaving an electrical resistance substantially less than that of each ofsaid outside strips, said bimetallic strips bending in response topassage of current v'therethrough and being arranged sothat the concavesides of said outside strips face respectively toward and away from saidintermediate strip.

l2. In a circuit breaker, -a thermally responsive element comprising agroup of. at least three birnetallic strips assembled in substantiallyparallel relationship and in series circuit arrangement, there being twooutside strips and one intermediate strip, said intermediate striphaving an electrical resistancesubstantially less than that of each ofsaid outside strips whereby the rate o of bending of said outside stripsdue to passage of current through said element is greater than that ofsaid intermediate, said strips being so related to one another that theconcave sides of said outside strips face respectively toward and awayfrom said intermediate strip.

i3. In acircuit breaker. a thermally responsive element comprising threepairs of bimetallic strips assembled in substantially parallelArelationship, means for electrically connecting and mechanically joiningadjacent ends of the rst pair of strips, means electrically connectingand mechanically joining adjacent ends of the second pair of strips tothe other adjacent ends of said rst pair of strips; means forelectrically connecting and mechanically joining adjacent ends of thethird pair of strips to the other adjacent ends of said second pair ofstrips, means for connecting the remaining adjacent ends of said thirdpair of strips in series with the circuit, and means for securing saidremaining ends to a support, said bimetallic strips bending'in responseto passage of current therethrough and being arranged so that theconcave sides of all of said strips face in the same direction.

14. In a circuit breaker, a thermally responsive element comprisingthree pairs of bimetallic strips assembled in substantially parallelrelationship, means for electrically connecting and mechanically joiningadjacent ends of the fir-st pair of strips, means electricallyconnecting and mechanically joining adjacent ends of .the second pair orstrips to the other adjacent ends of said first pair of strips, meansfor electrically connecting and mechanically joining adjacent ends ofthe third pair of strips to the other adjacent ends of said second pairof strips, means for connecting the remaining adjacent ends of saidthird pair of strips in series with the circuit, and means for securingsaid remaining ends to a support, said bimetallic strips bending inresponse to current therethrough and being arranged so that the concavesides of said second pair of strips faces the convex sides of said rstpair of strips and the convex sides of said second pair of strips facesthe concave sides of said third pair oi strips.

l5. In a circuit breaker, a thermally responsive element comprisingthree pairs of bimetalllc stripsl assembled in substantially parallelrelationship, means for electrically connecting and mechanically joiningadjacent ends of the first pair of strips, means electrically connectingand mechanically joining adjacent ends of the second pair of strips rtothe other adjacent ends of said rst pair of strips, means forelectrically connecting and mechanically joining adjacent ends oi thethird pair of strips to the other adjacent ends of said second pair ofstrips, means for connecting the remaining adjacent ends of said thirdpair of strips in series with the circuit, and means for securing saidremaining ends to a support, said bimetallic strips bending in responseto current therethrough and being arranged so that the concave sides ofsaid second pair of strips faces the convex sides of said rst pair ofstrips and the convex sides of said second pair of strips faces theconcave sides of said third pair of strips, and means responsive to saidbending for shuntcircuiting said element.

16. A high voltage circuit breaker comprising spaced upper and lowerterminals, an upwardly extending hollow tube of insulating materialspanning said terminals and movable between closed and open positions,a` conductor within said tube, a current responsive element mountedexternally of said tube at the upper end thereof, means including theserial arrangement of said conductor and said current responsive elementfor electrically connecting said terminals when said breaker is in theclosed position, and means responsive to passage of a predeterminedcurrent through said current responsive element for contemporaneouslywithdrawing said conductor fromv said tube at the lower end thereof andmoving the upper end of said tube away from the upper terminal to theopen position whereby said current responsive element is electricallyisolated with respect to each of said terminals when said breaker is inthe open position.

RALPH R. PI'ITMAN. CARROIL H. WALSH.

